Ellipsometric characterisation of Langmuir monolayer of “hairy-rod” polymeres at the air-water interface

Abstract

Surface pressure versus area (pi-A) diagrams of various poly(gamma-methyl-L-glutamate-co-gamma-alkyl-L-glutamates) are presented together with their simultaneously recorded ellipsometric \DELTA-DELTA-H2O\ isotherms. These materials are representatives of the class of hairy-rod polymers. Ellipsometry is very sensitive toward changes in the refractive index and the thickness of the monolayer and therefore provides valuable information about the physical properties of the film. The combination of both techniques makes it possible to identify the characteristic broad plateaus occuring in the pi-A diagrams. Furthermore, the lateral homogeneities of the monolayers in the various phases were investigated by scanning the laser spot across the Langmuir trough. All phases except the plateau region turned out to be laterally homogeneous. In this region the formation of an undefined monolayer piling up in front of the barrier was detected.